Hi all,

 

Was fitting new shocks and springs to the rear of my Octavia, and I crossthreaded the bolt which goes through the bottom of the shock - I measured the bolt with a caliper and it said 13mm, but wondered if anyone knew exactly what type of bolt this was? Then I can order a tap/die for exactly that size.

 

Or any 'hacks' I can try to fix?

 

It's a pain because that hole is closed/doesn't go through the otherside, so I guess is harder to rethread?

 

Annoying as we're supposed to be driving to the peak District at the weekend!

Helicoil insert ?.

 

Lots on sale and there are plenty of sites on how to fit them .

9 minutes ago, erindad said:

Helicoil insert ?.

 

Lots on sale and there are plenty of sites on how to fit them .

Would I use that as well as the tap/die? Bit confused to the benefits of it?

13mm hexagon would normally be an M8x1.25 ISO standard thread.

 

You dont normally retap a crossed thread, too big a risk of the tap following the crossed thread and breaking especially if it is Chinesium.

 

Usually a new bolt held concentric when tightening will usually thread straight, you can ease its passage by removing the first few threads by machining or grinding/filing to make a spigot to lead the thread, then you can fit a full threaded bolt.

31 minutes ago, RobSuf said:

exactly what type of bolt this was

According to the parts catalogue for an '07 combi/estate HERE it's M14 x 1.5 x 70, although it doesn't say if the bolt is high tensile or not.

25 minutes ago, erindad said:

Helicoil insert ?.

 

Lots on sale and there are plenty of sites on how to fit them .

Not needed and likely to cause even more problems for someone who can cross thread a bolt.

47 minutes ago, MikeTheThinker said:

According to the parts catalogue for an '07 combi/estate HERE it's M14 x 1.5 x 70, although it doesn't say if the bolt is high tensile or not.

Google imaging the WHT version of those part numbers suggests it is a 10.9 grade, so yes.

Take a look at this LINK for skoda-parts.com which shows the bolt in question plus a list of all Octavias it fits (and it looks like all mk2s).

What about a replacement arm from a scrap yard, and a new bolt?

 

Just an alternative option.

 

Gaz

Thank you all for the ideas, in the end copious amounts of copper grease allowed me to get it done up tight.. it's a high miler so hopefully it will be it's last set of shocks so I don't have to undo it again lol

To anyone else reading, - that is absolutely not the way to deal with a cross threaded bolt especially on a safety related component.

17 hours ago, J.R. said:

Not needed and likely to cause even more problems for someone who can cross thread a bolt.

 

Literally every member of this forum has cross threaded a bolt at some point, no need to be condescending. 

 

1 hour ago, J.R. said:

To anyone else reading, - that is absolutely not the way to deal with a cross threaded bolt especially on a safety related component.

 

If it works it works. It's tight as hell and fully done up. Even if the car is still somehow alive long enough to need another new set of shocks, I'll still be in the same situation next time I need to undo it.

7 minutes ago, RobSuf said:

If it works it works. It's tight as hell and fully done up.

May I suggest you treat it as you would treat wheel studs/nuts after refitting; check them after a couple of hundred miles for tightness and - especially in this case where there is only one fastener holding things together, and not four or five - continue to check at appropriate intervals.  Regardless of your success in managing to overcome the cross thread do keep in mind that the strength of the connection is now and never can be up to the level of the original undamaged part.

1 hour ago, RobSuf said:

If it works it works. It's tight as hell and fully done up.

 

Cross threaded and greased.

 

1 hour ago, RobSuf said:

Literally every member of this forum has cross threaded a bolt at some point, no need to be condescending. 

 

Indeed myself included but I always realised before any significant damage was done and  correctly refitted the fastener or a new fastener, only if the thread was stripped would I have resorted to a helicoil which being a machinist I knew how to do.

 

As you had asked if you should use a helicoil as well as a tap & die (the latter is for male threads) I (correctly as it turns out) made a judgement of your knowledge and capabilities, I realised you might take exception to the comment but I was trying to save you from yourself, given your confidence in your final "solution" and especially the "LOL" I was not successful.

 

What is more important is that others would not  follow your lead believing it was the correct thing to do.

Edited 22 May, 20233 yr by J.R.

7 minutes ago, J.R. said:

 

Cross threaded and greased.

 

 

Indeed myself included but I always realised before any significant damage was done and  correctly refitted the fastener or a new fastener, only if the thread was stripped would I have resorted to a helicoil which being a machinist I knew how to do.

 

As you had asked if you should use a helicoil as well as a tap & die (the latter is for male threads) I (correctly as it turns out) made a judgement of your knowledge and capabilities, I realised you might take exception to the comment but I was trying to save you from yourself, given your confidence in your final "solution" and especially the "LOL" I was not successful.

 

What is more important is that others would not  follow your lead believing it was the correct thing to do.

 

I'm sure you're probably correct - but no need to be so insufferable

 

On the plus side everything is torqued down and job finished now, will check the torque in a few days 👍

It'll be fine. 

2 hours ago, RobSuf said:

Literally every member of this forum has cross threaded a bolt at some point......

 

Oh no I didn't 😇

 

Anyway, nobody saw me.  It was the big boy, and he ran off that way 👉

 

G

 

28 minutes ago, RobSuf said:

but no need to be so insufferable

 

Equally no need to call people names, we are all adults here and contributing to the community to help others.

A tip in the case of crossed threads - especially if just at the first few threads of the tapping - with a non-stripped bolt, cut two or three angled grooves across the threads at the end of the bolt with a fine-blade hacksaw and use it to 'clean up' the starting threads while very carefully keeping the bolt in correct alignment.

With a HT bolt, this can serve as a tap if the thread isn't too badly damaged.     

2 hours ago, MikeTheThinker said:

Regardless of your success in managing to overcome the cross thread do keep in mind that the strength of the connection is now and never can be up to the level of the original undamaged part.

 

Indeed, the fastener has been subjected to a torsional load well beyond the Torque/Tension limit concentrated at the weakest point of the fastener, the transition of the rolled thread and the plain bolt shank, this is where an overtightened fastener would shear but from a tensile loading in a non cross threaded fastener, in this case it will have been a pure torsional loading which 10.9 spec bolts are absolutely not designed for, if it had gone beyond the elastic limit there will be surface cracking at the thread junction, this combined with the cyclical bending load of the suspension is the definitive recipé for fatigue failure.

6 minutes ago, Warrior193 said:

A tip in the case of crossed threads - especially if just at the first few threads of the tapping - with a non-stripped bolt, cut two or three angled grooves across the threads at the end of the bolt with a fine-blade hacksaw and use it to 'clean up' the starting threads while very carefully keeping the bolt in correct alignment.

With a HT bolt, this can serve as a tap if the thread isn't too badly damaged.     

 

Indeed, that is what I usually do with the sacrificial fastener after removing the first few threads to act as a guide.